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Employee Benefit Plans - Schedule of Pension Plan Assets at Fair Value (Detail) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | --- | ---
Insurance contracts |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | $ 8 | $ 8 | $ 8
Recurring |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 72 | 69 |
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 0 | 0 |
Recurring | Significant Other Observable Inputs (Level 2) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 64 | 61 |
Recurring | Significant Unobservable Inputs (Level 3) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 8 | 8 |
Recurring | Money market funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 1 | 1 |
Recurring | Money market funds | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 0 | 0 |
Recurring | Money market funds | Significant Other Observable Inputs (Level 2) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 1 | 1 |
Recurring | Money market funds | Significant Unobservable Inputs (Level 3) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 0 | 0 |
Recurring | Equity funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 25 | 23 |
Recurring | Equity funds | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 0 | 0 |
Recurring | Equity funds | Significant Other Observable Inputs (Level 2) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 25 | 23 |
Recurring | Equity funds | Significant Unobservable Inputs (Level 3) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 0 | 0 |
Recurring | Bond/fixed-income funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 32 | 30 |
Recurring | Bond/fixed-income funds | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 0 | 0 |
Recurring | Bond/fixed-income funds | Significant Other Observable Inputs (Level 2) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 32 | 30 |
Recurring | Bond/fixed-income funds | Significant Unobservable Inputs (Level 3) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 0 | 0 |
Recurring | Real estate indirect investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 6 | 7 |
Recurring | Real estate indirect investments | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 0 | 0 |
Recurring | Real estate indirect investments | Significant Other Observable Inputs (Level 2) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 6 | 7 |
Recurring | Real estate indirect investments | Significant Unobservable Inputs (Level 3) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 0 | 0 |
Recurring | Insurance contracts |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 8 | 8 |
Recurring | Insurance contracts | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 0 | 0 |
Recurring | Insurance contracts | Significant Other Observable Inputs (Level 2) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | 0 | 0 |
Recurring | Insurance contracts | Significant Unobservable Inputs (Level 3) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets at fair value | $ 8 | $ 8 |

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